Using SOLVE command with syms

GAGANDEEP KAUR

2020 11 2

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I also need to determine some variables using syms with solve command but find some issue with syms itself.

Code is like this:

for i=1:9

syms a b c d e ;

%calculating mole fractions of ionic species

x1=[0.5096 0.5092 0.5087 0.4852 0.4847 0.4834 0.4804 0.4805 0.4803];

x2=[0.0963 0.0964 0.0965 0.1163 0.1161 0.1158 0.1275 0.1266 0.1253];

x3=[0.3941 0.3944 0.3948 0.3985 0.3992 0.4008 0.3921 0.3929 0.3943];

T=[394.15 399.15 404.15 375.15 390.15 405.15 374.15 392.15 406.15];

%Equilibrium constant for reaction 1 (Solvation reaction)

K1=exp((-8.549)+(6692/T(i)));

%Equilibrium constant for reaction 2(Ionization of water)

K2=10^(-14);

%Equilibrium constant for reaction 3(Dissociation of HI)

K3=exp((16.93565)+((1250)/T(i))+(-2.575*log(T(i))));

%Equilibrium constant for reaction 4(Polyiodide formation a)

K4=exp((-936.28)+((40216.27)/T(i))+(151.983*(log(T(i))))+(-0.1675*(T(i))));

%Equilibrium constant for reaction 5(Polyiodide formation b)

K5=exp((1044.78)+(-45171.42/T(i))+(-165.20*log(T(i)))+(0.1511*(T(i))));

eqns=[((d*(c-e))/((x1(i)-a-b-c-d)^5)*(x2(i)-d-b-c))==K1,((a+b+c)*a)/((x1(i)-a-b-c-d)^2)==K2,(((a+b+c)*(d+b))/((x1(i)-a-b-c-d)*(x2(i)-d-b-c-e)))==K3,(((a+b+c)*(c-e))/((x1(i)-a-b-c-d)^4*(x2(i)-d-b-c-e)))==K4,(((e)*(x1(i)-a-b-c-d)^3)/((c-e)*(x3(i)-e)))==K5];

S=solve(eqns,a, b, c, d, e)

S.a(S.a<0)=[];

S.b(S.b<0)=[];

S.c(S.c<0)=[];

S.d(S.d<0)=[];

S.e(S.e<0)=[];

S.a=double(S.a);

S.b=double(S.b);

S.c=double(S.c);

S.d=double(S.d);

S.e=double(S.e);

end